Half the world’s river volume is affected by flow alterations and/or fragmentation, a figure that is likely to increase with the current global surge in hydropower development. At the same time, freshwater biodiversity is in rapid decline. In fluvial ecosystems, streamflow is a master variable, shaping riverine species’ habitat over space and time. Atlantic salmon (Salmo salar) and brown trout (S. trutta) are examples of species that need fluvial habitats for reproduction and juvenile rearing, and whose flow needs can come in conflict with hydropower production objectives. This necessitates tools for predicting the effect of fluvial habitat alteration on fish production. In this thesis, I applied the individual-based model inSTREAM to simulate salmon and trout in the Gullspång Rapids, a residual flow stretch of the Gullspång River, Sweden, over a ten-year period. InSTREAM uses sub-daily time steps to simulate individual fish interacting with their biotic and physical environment, and tracks the fitness consequences of their main actions: habitat and activity selection. For inSTREAM input, I had to describe key habitat features, create a 2D hydraulic model of the rapids, model river temperature, and gather data on salmon and trout eco-physiology and life history characteristics in the Gullspång River. I ran simulation experiments varying either flow input, the number of spawners, spawning gravel, shelter and boulder availability, or temperature. Flow alterations had limited benefit. Only the scenario where the current minimum flow was set three times higher yielded increased production, and only for trout. Trout dominated salmon in competition, and production was density dependent. The model predicted that the only way to increase production of both species at current spawner numbers was to add instream structures offering more energetically profitable feeding positions. / Half the world’s river volume is affected by flow alterations and/or fragmentation –a figure that is likely to increase with the current global surge in hydropower development. Streamflow shapes the river habitat for species like Atlantic salmon (Salmo salar) and brown trout (S. trutta) –species that need rivers for reproduction and for juvenile rearing. In this thesis, I applied the individual-based model inSTREAM to simulate how salmon and trout interact with the physical and living environment in the Gullspång Rapids, a residual flow stretch in the Gullspång River, Sweden. InSTREAM follows individuals through spawning, egg development, and juvenile rearing until out-migration. I ran simulation experiments over ten years, varying either flow input, the number of spawners, spawning gravel, shelter availability, or temperature. Flow alterations had limited benefit; only in the scenario where the current minimum flow was tripled did production increase, and only for trout. Trout dominated salmon in competition for food and space, and production was density dependent. The model predicted that the only way to increase production of both species at current spawner numbers was to add instream structures offering more energetically profitable feeding positions. / <p>Article 2 part of thesis as manuscript, now published.</p>
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kau-76559 |
| Date | January 2020 |
| Creators | Lund Bjørnås, Kristine |
| Publisher | Karlstads universitet, Institutionen för miljö- och livsvetenskaper (from 2013), Karlstad |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Licentiate thesis, comprehensive summary, info:eu-repo/semantics/masterThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | Karlstad University Studies, 1403-8099 ; 2020:12 |
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